1. Field of the Invention
This invention is directed to a compression shear test jig, which is useful for determining the internal shear strength in the plane of a wood fiber or particle panel product. The principal object of the invention is to provide the wood fiberboard or particleboard producer, secondary manufacturer and researcher, a quick, simple and definitive means for determining the internal strength of these products so that internal bond and shear strength in the plane of the panel can be approximated. The jig is useful as a quality control tool for producers. Secondary manufacturers may use it to determine acceptability of shipments received. Research institutions find it useful for their research and developmental efforts.
2. The Prior Art
The standard test for determining the internal strength of wood fiberboard and particleboard is called the internal bond (IB) or tensile strength perpendicular to the surface test. It requires a specimen 2 in. square and of the thickness of the finished panel bonded on each face with suitable adhesive to 2 inch square loading blocks of steel, aluminum alloy or wood. A tensile load is applied at a uniform rate to the faces as nearly perpendicular as possible. The specimen is tested to failure in the weakest plane and the failing load is recorded.
Because fabrication of IB test specimens is time consuming and messy, there have been many attempts to devise alternative methods for approximating this property. However, each alternative has the disadvantage of either requiring gluing or not necessarily testing the specimen in the weakest plane.
Suchsland (Compression shear test for determination of internal bond strength in particleboard. Forest Products Journal 27(1): 32-36. 1977) discloses a test method based upon the basic engineering mechanics principle that an axial force develops maximum shear stress at an angle 45.degree. to the direction of the force. However, gluing of a test specimen is required. The gluing requirement of Suchsland's technique probably is the reason why it has not gained acceptance by the particleboard industry. Specimens to be tested by Suchsland's technique are parallelogram in shape and have the width dimension limited to the thickness of the test specimen. These are viewed as disadvantages. Although the Suchsland method embodies the test principle that forms the basis for this invention, these disadvantages are avoided with this invention.